Prospective studies carried out by the Precursors Study suggest the existence of psychological factors which precede the clinical appearance of premature disease or death by many years. We obtained an extensive, unique data base (psychological, psychosocial, physiological, medical and familial) on a cohort of 1,337 medical students and have followed them prospectively for 18 to 32 years. Now for the most part between the ages of 41 and 60, 68 of them have died, and more than 200 are living with serious disorders, including hypertension, coronary heart disease, cancer and mental illness. It is our aim: a. to study the enlarging disorder group in detail in an attempt to substantiate the youthful psychological characteristics we have already found in this cohort which appear to be potential predictors of several disease states; b. to search prospectively for new potential predictors within the psychological and behavorial data; c. to determine whether special clusters of predictive variables appear to be associated with particular types of disease; and d. to bring together the substance of the Precursors Study's findings to date.